Analysis and characterization of naphthenic acids by gas chromatography electron impact mass spectrometry of tert.-butyldimethylsilyl derivatives

The renewed interest in naphthenic acid (NA) as a wood preservative has driven the need for analytical techniques to characterize commercial supplies of NA. The compositional heterogeneity of NA makes analytical characterization extremely difficult. Fluoride ion chemical ionization mass spectrometry (FI-MS) has proven to be an effective technique in NA characterization. However, FI-MS is very complicated and expensive to perform. In this paper, an alternative to the FI-MS technique is presented which offers similar results with a more widely available bench-top electron impact (EI) mass spectrometer. By derivatization of NA components to their tert.-butyldimethylsilyl analogs, the extent of molecular fragmentation is greatly decreased and strong base peaks representing the unfragmented NA constituents are obtained in the EI spectra. Molecular mass and tentative structures can be deduced based on sites of unsaturation. (C) 1998 Elsevier Science B.V. All rights reserved.